1. Field of the Invention
The present invention relates to a heat-pump type air conditioning apparatus equipped with heat storage capability therein.
2. Description of the Prior Art
The conventional systems will be described which are known to date in a heat regenerative type heat-pump air conditioning apparatus where a heat regenerative or ice storing refrigerant is also circulated to an air conditioning load side so as to perform a pleasant air conditioning.
One of such examples for the conventional systems is shown in FIG. 1 in which there are provided a plurality of indoor units, compressor 1 for compressing the refrigerant, 4-way valve 3 for switching a flow direction of the refrigerant at the time of cooling and heating, respectively, outdoor heat exchanger 5, a plurality of indoor heat exchangers 7, expansion valve 9, liquid tank 11, ice storage heating tank equipped with accumulator 13 and ice making unit 15, or the like. The path of the ice melting operation is shown by solid arrows. The path of the ice making operation is shown by dashed arrows. Outdoor heat exchanger 5 serves as a condenser at the time of cooling operation while it serves as an evaporator at the time of heating operation. On the contrary, indoor heat exchangers 7 serve as the evaporator at the time of cooling whereas it serves as the condenser at the time of heating. Expansion valve 9 serves to decrease the pressure of the refrigerant. Liquid tank 11 stores a refrigerant liquid
In the conventional system, a high-pressure liquid refrigerant that have flowed through outdoor heat exchanger 5 (serving as the condenser at the time of cooling) is further supercooled by ice making heat regenerative (storing) tank 17 so as to improve a cooling capacity. Such the conventional system thus described above is illustrated in a Mollier diagram shown in FIG. 2. With reference to FIG. 2, the capacity, say, approximately 10 horse power, of the outdoor unit can be gained to approximately 12 horse power thereof by an increased amount A due to the supercooling. In this case, an ice thawing operation for the supercooling is executed simultaneously with a normal cooling operation at all times. Approximately 20% of whole capacity accounts for one due to heat stored in the air conditioning system.
Now, in this type of the conventional air conditioning apparatus, ice making and heat regeneration are executed by utilizing an excess nightly power which is costwise effective. Then, the ice made and heat stored during night time is utilized for a cooling or heating during daytime. As a result thereof, a user can have an air conditioning bearing a relatively low running cost therefor; an electric power company that supplies the electric power to the users realizes to cut down on a peak for an electric power demand and tries to shift optimally a power peak during the daytime.
However, such conventional systems as mentioned above can only cut down on a whole capacity thereof by approximately as much as 20% in light of cutting down on the electricity, thus not being able to offer an effective means by which the power peak is shifted optimally. Moreover, in this case, the whole refrigerants being in a liquid state exist inside ice making unit 15 in heat regenerative tank 17, so that an amount of the refrigerant to be enclosed therein becomes undesirously large. Thus, the refrigerants are excessively supplied at other operational modes than that of the heat regenerative operation. Thereby, danger for the liquid bag is increased so as to effect the reliability for the air conditioning system. Moreover, such a system is not desirous in terms of global environment consciousness which recently enjoys a public consensus.
FIG. 3 shows another conventional air conditioning system.
In an another air conditioning system shown in FIG. 3, a circuit having heat regenerative tank 17 and refrigerant pump 19 is incorporated therein in parallel to the refrigerant circuit of normal indoor heat exchanger 7 shown in FIG. 1. Thereby, both the cooling operation by compressor 1 and the refrigerant transfer by refrigerant pump 19 can be independently or simultaneously executed. Not to mention, the ice making operation is carried out by compressor 1.
In the air conditioning system shown in FIG. 3, a low power cooling operation can be realized utilizing refrigerant pump 19 by stopping compressor 1 after the ice making operation. The low power cooling operation is illustrated by a solid line shown in FIG. 4. Thereby, a power peak value is reduced, so as to off tier means for effectively shifting the power peak. In FIG. 4, a broken line shows a cycle at the time of the normal cooling operation.
With reference to the solid line shown in FIG. 5, a heat regenerative operation becomes possible by storing hot water in heat storing tank 17 shown in FIG. 1 and FIG. 3. In FIG. 5, the broken lines show a cycle at the time of the normal heating operation. However, since there is utilized refrigerant pump 19, a temperature of the hot water gradually decreases, and finally the heating operation becomes inoperative. In other words, the hot water stored in the night time at a temperature as high as approximately 60.degree. C. can only be utilized up to approximately 40.degree. C. For the heating operation. Thus, there exists only a temperature difference of about 20.degree. C. which is too small a range to be effectively used. Thereby, time duration during which the heating operation is possible is rather short, thus creating a disadvantageous aspect where an efficient and effective heating operation can not be carried out.
Under the cooling operation period, an increase of the capacity for the outdoor unit can be possible by simutaneously operating both refrigerant pump 19 and compressor 1, thus possibly realizing the increase of an installment capacity for the outdoor unit. However, in case of the heating operation, the installment capacity for the outdoor unit can not be reduced due to the fact that an amount of the heat stored is not enough. Thus, there is caused an disadvantageous aspect in the light of imbalance of capacities between the cooling operation and the heating operation.
Accordingly, in the conventional air conditioning systems, it is impossible to perform an effective peak-cut operation where the electric power peak is effectively shifted optimally. Moreover, even if such a peak-cut operation is possible, there is still a problem where the heat regenerative operation can not be effectively performed at the time of heating operation and there exists imbalance of capacities between the cooling operation and the heating operation.